Label distribution protocol (LDP)

The Label Distribution Protocol (LDP) establishes MPLS LSPs using the existing IP routing network. ENA provides a detailed inventory of LDP distribution within its managed network. You can view a series of tabs including a breakdown of LDP configuration and current performance:

MPLS LDP Entity

MPLS LDP Entity Status

MPLS LDP Peers

MPLS LDP Peer Status

MPLS LDP Label Ranges

MPLS LDP Label Range MPLS LDP Peers

MPLS LDP Label Range Ports.

ENA MPLS includes a set of events which monitor this polled data, providing clear insight into changes and possible problems with your LDP distribution. Events are raised against these measures, event thresholds are configurable:

MPLS LDP Entity Errors

MPLS LDP Entity Operational Status

MPLS LDP Entity Rejected Sessions

MPLS LDP Entity Shutdown Notifications Received

MPLS LDP Entity Shutdown Notifications Sent

MPLS LDP Peer Disappeared

MPLS LDP Peer Newly Discovered

MPLS LDP Peer Operational Status

MPLS LDP Peer TLV Errors

MPLS LDP Peer Unknown Message Types

ENA MPLS includes a series of key reports:

LDP Inventory Detail Report

LDP Inventory Summary Report

LDP Label Range Report

LDP Peer Performance Report

You can also create new reports.

LDP Overview

LDP is a set of procedures by which one LSR informs another of the meaning of labels used to forward traffic between and through them. It is through LDP that LSRs establish Label Switched Paths (LSPs). LSPs are also known as MPLS tunnels.

To maintain the Label Switched Router (LSR) database MPLS labels must be distributed.

LDP associates a Forwarding Equivalence Class (FEC) with each LSP it creates. The FEC associated with an LSP specifies which packets are handled by that LSP.

An LSP starts at the Label Edge Router (LER), which assigns the first label to the packet determined by the FEC. The LER then forwards the packet to the next router in the path, which swaps the packet's outer label for another label, and forwards it to the next router. The last router in the path removes the label from the packet and forwards the packet based on the header of its next layer, for example IPv4.

LDP Peers are two LSRs which use LDP to exchange label/FEC mapping information. This exchange takes place during an LDP session.

MPLS LDP entity general attributes

Attribute

Description

Label Retention Mode

when configured to:

Conservative, the advertised label mappings are retained only if they will be used to forward packets, i.e. if label came from a valid next hop.

Liberal, then all advertised label mappings are retained whether they are from a valid next hop or not.

Threshold for Session Initiation Attempts

when set to:

0 indicates that the threshold is infinity, and so effectively the SNMP notification is disabled.

1 or greater, the LDP entity sends an mplsLdpFailedInitSessionThresholdExceeded when the number of session initialization messages sent exceeds this threshold.

Label Distribution Method

when the LSR is using:

Downstream Unsolicited distribution it advertises FEC-label bindings to its peers when it is ready to forward packets in the FEC by means of MPLS.

Downstream on Demand distribution provides FEC-label bindings to a peer in response to specific requests from the peer for a label for the FEC.

LDP Protocol Version

version number of the protocol. When set to 0, this indicates that the version of the protocol is unknown.

Hop Count Limit

maximum allowable number of hops permitted, applicable when Loop Detection Capability must be set to either Hop Count And Path Vector or Hop Count.

LDP TCP Discovery Port

LDP TCP port 646 used for establishing transport connection.

PVL Mismatch Traps Enabled

the mplsLdpPathVectorLimitMismatch notification is generated when there is a mismatch in the Path Vector Limits between the Entity and Peer during session initialization. The session uses the value which is configured as the Entity's Path Vector Limit. However, a notification should be generated to indicate that a mismatch occurred.

Hello Hold Time

value which is the proposed Hello hold time for this LDP Entity. A value of 0 means use the default, which is 15 seconds for Link Hellos and 45 seconds for Targeted Hellos. A value of 65535 means infinite.

Is Targeted Peer

when set to:

true, the LDP entity uses targeted peers

false the LDP entity does not uses targeted peers.

Targeted Peer Address

address used for the Extended Discovery.

Maximum PDU Length

maximum PDU Length that is sent in the Common Session Parameters of an Initialization Message. A value of 255 or less specifies the default maximum length of 4096 octets.

Keep Alive Hold Time

value which is the proposed keep alive hold timer for this LDP Entity.

LDP UDP Discovery Port

UDP port, by default 646, used with the discovery message.

Path Vector Limit

When set to:

0, loop detection for path vectors is disabled.

a value greater than zero, loop detection for path vectors is enabled, and the Path Vector Limit is this value.

For the Path Vector Limit to have effect the device’s Loop Detection Capability must be set to either Hop Count And Path Vector or Path Vector.

MPLS LDP entity stream attributes

Attribute

Description

Admin Status

Administrative status of this LDP entity. When set to:

Enable, the entity can create new sessions with its peer.

Disable, any existing peer connections are lost. When set to disable, the administrator can amend the entity values.

Oper Status

operational status of the LDP entity, which can be:

Unknown, this should only be a transitional state.

Enabled.

Disabled.

Attempted Sessions

total number of attempted sessions for this LDP Entity.

Rejects (No Hello)

count of the Session Rejected/No Hello Error Notification Messages sent or received by the LDP entity.

Rejects (Bad Ad.)

a count of the Session Rejected/Parameters Advertisement Mode Error Notification Messages sent or received by this LDP Entity.

Rejects (PDU Length)

a count of the Session Rejected/Parameters Max Pdu Length Error Notification Messages sent or received by this LDP Entity.

Rejects (LR)

a count of the Session Rejected/Parameters Label Range Notification. Notification Messages sent or received by this LDP Entity.

Bad Identifier

number of Bad LDP Identifier Fatal Errors detected by the session(s) (past and present) associated with this LDP entity.

Bad PDU Length

number of Bad PDU Length Fatal Errors detected by the session(s) (past and present) associated with this LDP Entity.

Length Errors

number of Bad Message Length Fatal Errors detected by the session(s) (past and present) associated with this LDP entity.

TLV Length Errors

number of Bad TLV Length Fatal Errors detected by the session(s) (past and present) associated with this LDP entity

Bad TLV Values

number of Malformed TLV Value Fatal Errors detected by the session(s) (past and present) associated with this LDP entity.

Keep Alive Timeouts

number of Session Keep Alive Timer Expired Errors detected by the session(s) (past and present) associated with this LDP entity.

Shutdowns Received

number of Shutdown Notifications received related to session(s) (past and present) associated with this LDP entity.

Shutdowns Sent

number of Shutdown Notifications sent related to session(s) (past and present) associated with this LDP entity.

Rejected Sessions Delta

change in the number of rejected sessions between the two most recent pollings.

Error Delta

change in the number of errors between the two most recent pollings.

Shutdowns Received Delta

change in the number of shutdowns received between the two most recent pollings.

Shutdowns Sent Delta

change in the number of shutdowns sent between the two most recent pollings.

MPLS LDP peers

The connection from the local LDP entity to an LDP peer is through to the remote LDP entity. Details of the remote peered LDP are as viewed from the local entity.

Attribute

Description

General

discovery details, e.g. advertised IP address.

MPLS LDP Label Ranges

supported label ranges.

MPLS LDP Entity

details of the remote entity.

Peer Status

key status metrics.

MPLS LDP peers general attributes

Attribute

Description

Path Vector Loop Detection

indicates whether loop detection based on path vectors is disabled or enabled for this LDP peer.

Advertised IP

IP address advertised to its LDP peers.

Path Vector Hop Limit

when set to:

0, loop detection for path vectors is disabled.

a value greater than zero, loop detection for path vectors is enabled, and the Path Vector Limit is this value.

For the Path Vector Hop Limit to have effect, the device's Loop Detection Capability must be set to either Hop Count And Path Vector or Path Vector.

Label Distribution Method

when the LSR is using:

Downstream Unsolicited distribution, it advertises FEC-label bindings to its peers when it is ready to forward packets in the FEC by means of MPLS.

Downstream on Demand distribution, it provides FEC-label bindings to a peer in response to specific requests from the peer for a label for the FEC.

MPLS LDP label ranges

Attribute

Description

Name

name of the label range.

IF Index

interface index of the outgoing label of this LSP.

Maximum Label

upper boundary of the label range.

Minimum Label

lower boundary of the label range.

MPLS LDP peer status

Attribute

Description

Status

polled state of the session, i.e. Non-existent, Initialized, Open receive, Open sent and Operational.

LDP Version

version number of the protocol. When set to 0, this indicates that the version of the protocol is unknown.

Peer Max PDU Length

maximum PDU length that is sent in the Common Session Parameters of an Initialization Message. A value of 255 or less specifies the default maximum length of 4096 octets.

Unknown Message Type Errors

number of Unknown Message Type Errors detected during this session. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of mplsLdpSeeionDiscontinuityTime.

Unknown TLV Errors

number of Unknown TLV Errors detected during this session. Discontinuities in the value of this counter can occur at re-initialization of the management system, and at other times as indicated by the value of mplsLdpSeeionDiscontinuityTime.

MPLS LDP label range MPLS LDP peers

Attribute

Description

Name

name of the MPLS LDP peer.

Path Vector Loop Detection

indicates whether loop detection based on path vectors is disabled or enabled for this LDP peer.

Advertised IP

IP address that is advertised to its LDP peers.

Path Vector Hop Limit

when set to:

0, loop detection for path vectors is disabled.

a value greater than zero, loop detection for path vectors is enabled, and the Path Vector Limit is this value.

For the Path Vector Hop Limit to have effect, the device's Loop Detection Capability must be set to either Hop Count And Path Vector or Path Vector.

Label Distribution Method

when the LSR is using:

Downstream Unsolicited distribution, it advertises FEC-label bindings to its peers when it is ready to forward packets in the FEC by means of MPLS.

Downstream on Demand distribution provides FEC-label bindings to a peer in response to specific requests from the peer for a label for the FEC.

Label switch routers

Label Switch Routers (LSRs) support MPLS. LSRs originate the Label Switch Path (LSP). The ingress LSR computes the path for a given LSP. The egress router is the point of output from the LSR.

MPLS LSR

The label space can be set at the platform or interface space. You can also view the LSR configuration at both the device and interface level.

Attribute

Description

Min label (RX)

minimum value of an MPLS label that this LSR is willing to receive on this interface.

Max label (RX)

maximum value of an MPLS label that this LSR is willing to receive on this interface.

Min label (TX)

minimum value of an MPLS label that this LSR is willing to send on this interface.

Max label (TX)

maximum value of an MPLS label that this LSR is willing to send on this interface.

Usable Bandwidth

total amount of usable bandwidth on this interface and is specified in kilobits per second (Kbps). This variable is not applicable when applied to the interface with index 0.

Available Bandwidth

total amount of available bandwidth available on this interface - specified in kilobits per second (Kbps). This value is calculated as the difference between the amount of bandwidth currently in use and that specified in mplsInterfaceTotalBandwidth. This variable is not applicable when applied to the interface with index 0.

Allocated Space

total amount of buffer space allocated for this interface. This variable is not applicable when applied to the interface with index 0.

Available Space

total amount of buffer space available for this interface. This variable is not applicable when applied to the interface with index 0.

Label Space

either set to per Platform(0) or per Interface(1). When the value is:

perInterface(1) bit is set then the value of Min label (RX), Max label (RX), Min label (TX), and Max label (TX) for this entry reflect the label ranges for this interface.

perPlatform(0) bit is set, then the value of value of Min label (RX), Max label (RX), Min label (TX), and Max label (TX) for this entry must be identical to the instance of these objects with index 0.

Labels In Use (RX)

number of inbound labels used.

Packets (RX)

number of labeled packets that have been received on this interface.

Error Free Discards (e.g. insufficient buffer)

number of outbound labeled packets, which were chosen to be discarded even though no errors had been detected to prevent their being transmitted. One possible reason for discarding such a labeled packet could be to free up buffer space.

Lookup Failure Discards

number of labeled packets that have been received on this interface and were discarded because there were no matching entries found for them in mplsInSegmentTable.

Labels In Use (TX)

number of top-most labels in the outgoing label stacks that were in use on this interface.

Packets (TX)

number of labeled packets that have been transmitted on this interface.

Error Free Discards (TX)

number of outbound labeled packets, which were chosen to be discarded even though no errors had been detected to prevent their being transmitted. One possible reason for discarding such a labeled packet could be to free up buffer space.

Packets Fragmented

number of outgoing MPLS packets that required fragmentation before transmission on this interface.

RX Discard No Error Pkt Rate

difference between two contiguous inbound Error Free Discards sampled values, as a per second average.

TX Discard No Error Pkt Rate

difference between two contiguous outbound Error Free Discards sampled values, as a per second average.

RX Discard Lookup Failure Pkt Rate

difference between two contiguous inbound Packets (Rx) sampled values, as a per second average.

TX Pkt Fragmentation Rate

difference between two contiguous outbound Packets Fragmented sampled values, as a per second average.

MPLS VPN

A network with an MPLS backbone provides the flexibility to deliver high value VPN services. The Provider Edge (PE) router provides a different, private view of the network to each VPN. This allows for different customers to use the same network resources, using different addressing to gain secure, customer specific routing. This separation is realized through separate VRF instances on a PE behaving as separate router emulations.

These Virtual Routing and Forwarding Tables (VRF) are dedicated routing tables for Layer 3 VPNs containing IP prefixes. ENA can monitor the performance of VRF instances through monitoring the success or failure of its route target distribution.

MPLS VRF general

ENA gathers MPLS configuration data from every MPLS-enabled port.

Attribute

Description

VRF Name

VRF name.

VRF Description

description of the VRF, e.g. its purpose.

VRF High-Water Route Threshold

denotes high-level water marker for the number of routes which this VRF may hold.

VRF Mid-Water Route Threshold

denotes mid-level water marker for the number of routes which this VRF may hold.

VRF Route Distinguisher

route distinguisher that makes the VRF unique, distinguishing between overlapping addresses in the VRF.

VRF Maximum Routes

maximum number of routes on the VRF. It must be less than or equal to the maximum possible number of routes, unless it is set to 0.

MPLS route targets

Route targets are used as targets for routing updates. The VRF RTs tab shows all of the routing targets associated with all instances of the VRF.

Attribute

Description

Name

name of the route target distribution policy.

Route Target

route target identifier.

Description

description of the route target.

Type

import/export distribution policy for the route target, i.e. import, export, and import and export. The configuration of the VPN topology is determined through the Type setting of VRFs.

MPLS VRFs status

Attribute

Description

Oper status

operational status of the VRF. When it is set to:

Up, one or more interfaces associated with the VRF is up.

Down, there are no interfaces associated with the VRF, or all interfaces associated with the VRF are down.

Active Interface

number of interfaces associated with the VRF that are up.

Associated Interface

number of interfaces associated with the VRF, including both active and inactive interfaces.

Routes Added

number of routes added over the lifetime of the VRF.

Routes Deleted

number of routes deleted over the lifetime of the VRF.

Routes

number of routes currently used by this VRF.

Illegal labels

number of illegal label violations on the interface. These may indicate MPLS misconfiguration, or an attempt to breach network security.

Illegal labels Threshold

illegal label violation threshold.

Illegal label Violation Rate

number of illegal label violations per second.

MPLS interface VRF instances general

With MPLS you configure virtual routers, and within them divide a physical interface into multiple logical interfaces. For each logical interface you can assign a different VRF which can be for a different customer with a distinct FEC. You can configure routing send traffic to the appropriate virtual interface.

Attribute

Description

Name

identifies the VRF and its interface.

MPLS VRF Interface

VRF interface.

VRF Name

VRF name.

Classification

the VPN classification that denotes the context of the link, e.g. carrier-of-carrier's, enterprise, inter-provider.

Edge Type

either the provider edge (PE) or customer edge (CE) router.

RDP

VRF Interface Route Distribution Protocol across the PE-CE link, which can be:

dummy.

none.

BGP.

OSPF.

RIP.

ISIS.

other.

MPLS interface VRF BGP neighbors

This tab details the BGP neighbors of the VRF instance on the interface.

Attribute

Description

Name

resolved name, or IP address of the device.

Role

role played by this EBGP neighbor with respect to this VRF, e.g. CE.

Address

IP address of the EBGP neighbor.

VRF on an interface instance

This tab details the MPLS VRF associated with the virtual interface.

Attribute

Description

Name

VRF name.

VRF Description

description of the VRF, e.g. its purpose.

VRF High-Water Routes Threshold

high-level water marker for the number of routes which this VRF may hold.

VRF Mid-Water Routes Threshold

mid-level water marker for the number of routes which this VRF may hold.

VRF Route Distinguisher

route distinguisher for this VRF.

VRF Maximum Routes

maximum number of routes, summed across all VRFs, which the device allows. When set to 0, this indicates that the device is unable to determine the absolute maximum, and you could potentially set a configured maximum greater than that allowed by the device.